Device for preserving connecting bars for concrete structural members

ABSTRACT

A preserving element (5) formed as a synthetic material mould part has preserving troughs (6) in which the bent end sections (3b) of connecting bars (3), later to be bent out, are embedded with a brittle mass (7). The device has the advantage that after the anchoring of the connecting bars (at 3a) in the structural member (2), the element (5) and the mass (7) can be easily removed. The device forms an easily transported and handled structural unit which is usable in the production of construction joints of steel concrete structures of any kind.

The invention relates to a device for preserving connecting bars whichis fastened into the shuttering during the production of steel concretestructures and which exhibits an elongated preserving element in whichthe end sections of the connecting bars, to be bent out for connecting aconcrete structural member to be connected later, but first bentapproximately at right angles, are inserted.

In the production of concrete structures a distinction is made betweenspace joints (also called expansion joints) and construction joints.Whereas the former form a permanent delimitation of one structuralmember relative to another, the latter are necessary only for technicalreasons of execution; they are supposed to guarantee later on aforce-locking connection largely corresponding to the monolithicallycast members.

It is customary to make connecting bars a party to such a connection. Inorder not to have to provide for holes in the shuttering of theconstruction joint, through which holes such connecting bars extend, theportions of the connecting bars projecting from the structural member tobe first concreted are first bent approximately at right angles and arefastened to the shuttering or near the shuttering in such a way thatthey can be be bent out or back again after removal of the shuttering.In order at the same time to keep the bent portions of the connectingbars free of concrete and to facilitate the mentioned bending out andback, a device for preserving connecting rods is sometimes used, whichdevice is inserted in the shuttering and fastened and guarantees duringconcreting the formation of a cavity around the end sections of theconnecting bars to be bent out.

Such preserving devices are already known in various designs, amongothers from DE Patent Specification No. 2,307,073 and from CH PatentSpecification No. 562,376. The former of these prior publicationsdiscloses a preserving device which consists of preserving pieces,preserving front, and spacing strips lying between and is made of anelastically deformable material. The fabrication of this device is veryexpensive, but has the advantage of easy stripping off thefirst-concreted structural member. According to the second of theabove-mentioned two publications the preserving element consists of afoam material body in which the end sections of the connecting bars tobe bent out are embedded. This solution has found wide application;however, the scraping-out of the foam material necessary after strippingof the first-concreted structural member is time-consuming and involvesthe risk that residues, which disturb the force-locking connection ofthe following concrete member, remain stuck in the construction joint.

The task underlying the invention is to indicate for a preserving deviceof the above-described kind a formation which retains the advantages ofthe previously known embodiments without their disadvantages beinginherent therein. Production should not only be economical, but also theremoval of the device, no longer needed after stripping of thefirst-concreted structural member, should be able to take place quicklyand effortlessly.

The task is solved in that the preserving element consists mainly of athin-walled mould part formed of thermoplastic synthetic material(produced by the press-mould or deep-drawing method), in whichpreserving troughs open towards the flat side, receiving the endsections, are otherwise filled with an embedding mass, brittle in thehardened state, adhering neither to the connecting bars nor to thesynthetic material mould part, the device as a whole forming a rigidstructural unit of permanent shape.

As the embedding mass, silicate-base mixtures are used to advantage, asfor example plaster-sawdust mixture or aeroconcrete, the desiredproperties of which are widely controllable through additives, as forexample bentonite. The adhesion of the embedding mass to the concrete ofthe structural member can also be easily avoided by a coat of partingcompound, as for example white lime. For laying bare the connectingbars, it suffices to rip off the preserving element formed ofthermoplastic synthetic material after removal of the shuttering and,with a few hammer blows, to rid the end sections of the connecting barsof the brittle embedding mass.

In order to prevent the connecting bars and the embedding mass fromfalling out of the preserving element, it is advisable to provide forpreserving troughs having a dovetail cross-section, or to fasten flatsafety strips detachably to the preserving element across the preservingtroughs.

In a preferred embodiment it is provided for that on the flat side ofthe preserving element, elevations are formed which butt against theconvex side of the bending sections of the connecting bars projectingfrom the preserving troughs. It is thereby managed to keep the device asthin and thus also as light as possible, but at the same time also toachieve that no concrete lies upon the convex side of the bendingsections, which concrete would hinder their bending back.

In addition, provision may be made to provide the side of the safetystrips facing away from the embedding mass and/or the free surface ofthe embedding mass with a coating consisting of a cement settingretarder. By spraying away the non-set surface layer portions withwater, there then ensue on the first-concreted structural member roughsurfaces which promote a good bond in the construction joint beingformed later.

The invention is explained below by way of example with the aid of theenclosed drawing.

FIG. 1 shows a schematic top plan view of an embodiment of the deviceaccording to the invention, in which the end sections and, for the mostpart, also the bending sections of eight connecting bars are preserved,

FIG. 2 shows a perspective view of the preserving element belonging tothis device,

FIG. 3 shows a cross-section along the line III--III of FIG. 1, and

FIG. 4 shows a partial cross-section of a variant of execution of thepreserving element.

The device described here is inserted in shuttering 1, which is intendedfor a concrete structural member 2, and serves for preserving endsections 3b of the connecting bars 3 anchored by their U-shaped portions3a in this concrete structural member 2. It has an elongated,flat-bar-shaped preserving element 5 to be fastened, e.g., by nails 4,to the shuttering 1, in which element the mentioned end sections 3b ofthe connecting bars 3, to be bent out for connecting a concretestructural member to be connected later, rectilineal in this embodiment,are inserted according to the representation in FIGS. 1 and 3, namely bypairs in two rows in such a way that they overlap in each row, for whichpurpose the inserted end sections 3b of each pair are arranged at anacute angle to one another.

As is to be seen from FIG. 1, the end sections of six of the eightconnecting bars are directed towards the left, those of the twoconnecting bars which are depicted at the left-hand end of this FIG. 1are directed towards the right, overlying some of the end sectionsdirected towards the left. This arrangement results in a fullutilization of the length of the preserving element 5. All the endsections 3b are connected by bending sections 3c at approximately rightangles to the anchoring sections 3a intended to be anchored in theconcrete structural member 2.

The above-described arrangement of the end sections 3b largelydetermines the shape of two preserving troughs 6 which are formed in thepreserving element 5.

This last consists mainly of a thin-walled mould part formed ofthermoplastic synthetic material, as for example polystyrene, e.g. bythe press-mould or deep-drawing method, in which the preserving troughs6 are open towards the flat side 5a, from which the anchoring portions3a project. These troughs 6 receiving the end sections 3b are otherwisefilled with an embedding mass 7 which was doughy upon being put in butis brittle in the hardened state and adheres neither to the connectingbars nor to the synthetic material mould part, so that afterwards--asdescribed below--it can easily be removed. Suitable as the embeddingmass are, for example, silicate-base mixtures, such as plaster-sawdustor aeroconcrete; as already mentioned, bentonite or another additive maybe admixed. In its finished state the device forms a rigid structuralunit of permanent shape which can be easily transported, handled, andfastened to shuttering 1. The element 5 is provided with passage-holes 9for nails in its longitudinal edge regions.

On the preserving element 5 there is a jacket wall 5b running all aroundit, which the cover wall forming the flat side 5a adjoins. Formed in thelatter wall are elevations 5c, 5d, one wall portion of which--as isapparent from FIG. 2--lies in the continuation of a curved trough-wallportion and, together with the latter, butts against the convex side ofthe bending sections 3c of the connecting bars 3 projecting from thepreserving troughs 6. It is thereby achieved that cavities are formedbehind the bending sections 3c in the concrete of the structural member2 and thus the later bending-back of these sections is practically nothindered.

According to the representation in FIG. 3, the preserving troughs 6 havea cross-section broadening slightly from the bottom to the flat side 5a,which facilitates the forming-out of the preserving element 5 during itsproduction. Since, because of the lack of adhesion of the embedding mass7 to the preserving element, the danger would exist that it might fallout of the preserving troughs 6 together with the preserved connectingbars 3, flat safety strips 8, made for example of polystyrene, extendingacross the preserving troughs 6, resting in the region thereof againstthe embedding mass 7, are detachably fastened to the wall of the element5 forming the flat side 5a, e.g., by spot welding, adhesive connection,or by means of rivets, bolts, or the like.

In a variant of execution which is illustrated in FIG. 4, the preservingtroughs 6 might have a cross-section narrowing toward the flat side,e.g., trapezoidal, so that the embedding mass 7 is form-lockingly heldin them. With such a design, safety strips 8 may be dispensed with.

Adhesion of the embedding mass 7 to the structural member 2 can beavoided by a coating of the free surface of this mass with a partingcompound, as for example white lime.

The side of the safety strips 8 facing away from the embedding mass 7may have a profiling, e.g., a grooving, in order that the surfaceportions of the structural member 2 formed thereon receive acorresponding profiling, which contributes to the roughening of theconstruction joint obtained thereafter.

For the same purpose, this side and/or the free surface of the embeddingmass can be provided with a coating consisting of a cement settingretarder; the incompletely set surface layer portions on the structure 2can then be sprayed off with water after removal of the device.

After removal of the shuttering 1 and the preserving element 5, thebrittle embedding mass 7 is to be removed, which can take place byadministering some few hammer blows on the end sections 3b of theconnecting bars 3. Before or after the bending-out of these end sections3a into the rectilineal continuation of the legs of the anchored section3a, the possibly used safety strips 8 are also still to be taken away.

The device finds wide use in the production of construction joints insteel concrete structures of any kind, e.g., in the connection ofpartitions, steps, light-shafts, false floors, silo covers, etc., e.g.,to a main wall.

I claim:
 1. A reinforcement device adapted to be attached to a casing onwhich a steel-reinforced concrete structural member is to be made, saiddevice comprising an elongate holding element made substantially of athin-walled plastic mold, and reinforcing bars, the end portions ofwhich, bent-off approximately at right angles, are in said element, saidelongate holding element defining troughs open toward one side of theelement and receiving said end portions therein and cast in an embeddingmaterial which is brittle in its solidified state, but does not adhereeither to said reinforcing bars or to said element, said device being asa whole a rigid structural unit of permanent shape.
 2. A reinforcementdevice according to claim 1, wherein said bent-off portions have convexsides, and said one side of the elongated holding element is providedwith elevations against which said convex sides of the bent-off portionsof said reinforcing bars abut.
 3. A reinforcement device according toclaim 1, wherein the cross-sectional form of said troughs is convergenttowards the open side thereof.
 4. A reinforcement device according toclaim 1, including flat safety strips on said one side extendingtransversely across the troughs and resting on the solidified embeddingmaterial filling the troughs, said safety strips being detachablyconnected to said one side of the element.
 5. A reinforcement deviceaccording to claim 4, wherein each said safety strip has a side facingaway from the embedding material and said side is profiled.
 6. Areinforcement device according to claim 4, wherein said side of eachsafety strip facing away from the embedding material, and/or the freesurface of the embedding material, is provided with a coating ofconcrete loosening retarder.
 7. A reinforcement device adapted to beattached to a structure on which a metal reinforced concrete structuralmember is to be made, said device comprising an elongate holding elementincluding a thin-walled plastic mold device and metal reinforcing bars,the end portions of said reinforcing bars extending approximately atright angles to a center portion of the reinforcing bars, said elongateholding element defining a pair of longitudinally extending troughs opentoward one side of the element and receiving said end portions therein,said end portions being embedded in a brittle material that does notadhere either to said reinforcing bars or to said mold device, saidreinforcement device being a rigid structural unit.